I just posted this to a thread and thought I'd make it available to anyone who wants to run it on their servers. It changes all Default Addresses (i.e. catchall aliases) for all domains on the server to :fail:
Use at your own risk. That means, backup /etc/valiases before running it 
Code:
#!/usr/bin/perl
print "Converting all domain Default Accounts to :fail: ...";
opendir (DIR, "/etc/valiases/") or die;
while (my $file = readdir (DIR)) {
if ($file =~ /^\./) {next}
open (IN, "</etc/valiases/$file") or die;
my @data = <IN>;
close (IN);
open (OUT, ">/etc/valiases/$file") or die;
foreach my $line (@data) {
if ($line =~ /^\*\:/) {
print OUT "*: :fail:\n";
} else {
print OUT $line;
}
}
close (OUT);
}
print "Done!\n";
